Ceramic materials are used today in many applications which call for durable, tough, and heat-resistant materials. In making ceramic articles, a ceramic composite powder is often made by first wet mixing ceramic powder, such as aluminum nitride, with ceramic composite components, such as binders, lubricants, sintering aids, and other processing aids in a liquid medium.
Traditionally, when aluminum nitride powder is used as the ceramic powder, the wet mixing is performed using ethanol or some non-aqueous liquid as the liquid medium to aid in mixing. Water is generally not a suitable liquid medium for wet mixing with aluminum nitride powder because aluminum nitride is highly sensitive to hydrolysis. When aluminum nitride powder is hydrolyzed by water, undesirable aluminum hydroxides are formed on the powder, concomitant with an increased oxygen content.
However, due to environmental concerns, water would be an ideal liquid medium for wet mixing aluminum nitride powder with the other components. If water were to be used as the liquid medium, no precautions would need to be taken to avoid exposure to the liquid medium during wet mixing operations. Additionally, containment of the liquid medium and precautions to avoid the dangers of flammable liquids during and after mixing would not be necessary with water as it could be with other liquid mediums. Water also has the advantage of being relatively inexpensive and readily available.
It is a primary object of the present invention to provide aqueous compositions containing aluminum nitride powder which exhibit a reduced tendency for hydrolysis of the aluminum nitride contained therein and which may be comminuted, e.g., by ball-milling, without deleterious results.
It is also an object of the present invention to provide an easy method of processing aluminum nitride powder in water which exhibits a reduced tendency for hydrolysis of the aluminum nitride.